Combined service and emergency brake system apparatus



J. H. CLACK Jan. 16, 1968 COMBINED SERVICE AND EMERGENCY BRAKE SYSTEMAPPARATUS '7 Sheets-Sheet 1 Original Filed June 4, 1962 FIG.

INVENTOR. JAMES H GLA CK BY /p% Jan. 16, J. H. CLACK COMBINED SERVICEAND EMERGENCY BRAKE SYSTEM APPARATUS Original Filed June 4, 1962 7Sheets-Sheet 2 66v 1 J4 J6 6/ FIG. 3 157 66 3 3/ a 2/ a7 58 66\ f 0 a4 aI 1. mi /9- ,5/ .9a

INVENTOR.

JAM/55 HCLACK BY v J. H. CLACK Jan. 16, 1968 COMBINED SERVICE ANDEMERGENCY BRAKE SYSTEM APPARATUS 7 Sheets-Sheet Original Filed June 4,1962 FIG. 5

FIGVIO J. H. CLACK Jan. 16, 1968 COMBINED SERVICE AND EMERGENCY BRAKESYSTEM APPARATUS 7 Sheets-Sheet 4 Original Filed June 4, 1962 Jan. 16,1968 J. H. CLACK 3,363,519

COMBINED SERVICE AND EMERGENCY BRAKE SYSTEM APPARATUS Original FiledJune 4, 1962 7 Sheets-Sheet 5 LBIAS AIR IGNAL AIR EXH

l as I P l A I i65 12 I 1IIIIIIH 1 I 161 l6 1 fm Jan. 16, 1968 J. H.CLACK 3,363,519

COMBINED SERVICE AND EMERGENCY BRAKE SYSTEM APPARATUS Original FiledJune 4, 1962 7 Sheets-Sheet 6 Jan. 16, 1968 J. H. CLACK 3,363,519

COMBINED SERVICE AND EMERGENCY BRAKE SYSTEM APPARATUS Original FiledJune 4, 1962 7 Sheets-Sheet 7 k 284 2:35 286 2255 28? 284 A 1 280?? 2e1-285 i 2a2 United States Patent 3,363,519 COMBINED SERVICE AND ENERGENCYBRAKE SYSTEM APPARATUS James H. (Back, 2611 Niagara Way, Sacramento,Calif. 95826 Original application June 4, 1962, Ser. No. 199,813. Di-

vided and application Mar. 21, 1963, Ser. No. 267,398. Divided andapplication Dec. 30, 1963, Ser. No. 334,505, new Patent No. 3,272,566.Again divided and this appiication Apr. 25, 1966, Ser. No. 544,991

'10 Claims. (Cl. 92-130) This application is a division of applicationSer. No. 199,813, filed June 4, 1962, for Safety Brake System, nowabandoned, of application Ser. No. 267,398, filed Mar. 21, 1963, forCombined Service and Emergency Brake System Apparatus, now abandoned,and of application Ser. No. 334,505, filed Dec. 30, 1963, for CombinedService and Emergency Brake System Apparatus, now Patent No. 3,272,566,and relates to brake systems and associated apparatus for wheelsupported vehicles and more particularly the brake actuator unitsthereof. This invention is particularly useful for trucks, trailers,tractors and the like.

In the main, for normal service operation, trucks and trailers utilizebrakes operated by fluids such as air or hydraulic liquid. Generally,pressure developed by a pump or air compressor is transmitted throughappropriate control valves to apply braking forces on the wheels. By andlarge, these systems have worked well. However, rupture of pressurehoses, diaphragms, or mechanical breakdown of the compressor, pump or avalve have resulted, in the past, in disasters. Therefore, thesesystems, wherein fluid pressure is used to apply the brakes, oftentimesfurther employ mechanical brake mechanisms as a back-up for emergencyoperation. One emergency system, includes a cylinder and spring-loadedpiston connected in tandem to drive the same brake-shoe drivingconnection as operated by the fluid system. The spring is restrained bythe fluid pressure of the system. When the fluid pressure fails, thespring takes over to operate the driving connection. Thus, the drivingconnection is powered in service operation by fluid and in emergencyoperation by the spring. Arrangements of this kind have been referred toin the trade as piggyback units.

Piggyback units necessarily are rather long. Notwithstanding theirextended length, however, they can provide only a relatively shortthrow. A short throw can contribute to the problem of fading wherein,due to heating, the drums expand so as to place themselves out of reachof the shoes (linings). Furthermore, the use of large springs to applybraking forces has not been entirely satisfactory over an extended lifedue to their shorter flexing life as compared to smaller springs.

Air equipped systems also possess a seemingly inherent weakness, in thatmoisture tends to accumulate in the system. Extremely cold weather cancause this moisture to freeze and crucial operating components eitherwill not start to work until thawed or will, even worse, be permanentlydamaged. Also, rust and deterioration through dirt, grit and air-bornepollutants act to an accelerated degree on pneumatic braking systems.

It is generally an object of this invention to provide means foroperating the brakes of a wheel supported vehicle in a manner whichovercomes the foregoing and certain other problems of prior systems.

It is another object of the invention to provide a simplified means forapplying the brakes to a vehicle in both service and emergencyoperation.

It is another object of the invention to provide a brake 3,353,519Patented Jan. 16, 1968 actuator for a system in which the brakes areoperative any time the fluid pressure members are rendered inoperative,thereby providing a fail-safe system.

It is a more particular object of the invention to provide an actuatorfor a combination service and emergency brake system wherein energy foradvancing the brake shoes to brake applying condition during bothservice and emergency operation is derived substantially entirely byreleasing stored energy from a spring biasing means of the actuator.

Use of spring forces to apply the brake of a vehicle is inherently afaster acting approach to a fluid brake system and has a number of otherinherent advantages over systems where, for example, pneumatic pressureurges the brakes to brake applying position.

The objective of providing a service brake system using actuatorswherein spring forces act to apply the brakes under pneumatic orhydraulic control of the springs raises a number of problems, however.These problems, until now, have virtually relegated the use of springsin this manner to parking brake status.

Large forces must be available. As mentioned, however, springs ofsmaller size have a more desirable flexing life than the larger sizesand are, therefore, to be preferred. Further, to overcome the problem offading, the travel of the brake applying lever arm should be capable ofmoving through a relatively wide angle of displacement to fully rotatethe cam-ming element. This requires a rather extended movement of thebrake piston, inasmuch as the lever arm must be long enough to applysufficient braking forces'at the wheels using conventional fluidpressures in the system. Thus, the need for the presently used, ratherlong lever arms, is understandable, but imposes a correspondingly longactuator movement if fading is to be overcome.

In short, to use springs in a service system, among other requirementsthe springs should have good flexing characteristics under allconditions of temperature and provide a long actuator movement.

In addition, spring generated forces must provide trouble-freemaintenance and avoid unsatisfactory diminution of force at fulldisplacement of the actuator.

It is generally considered that helical springs tend to break fromfatigue midway between their ends. I have observed, however, that thepoint of fracture is more properly to be identified with the midpointbetween the sprung and unsprung masses that are separated by thesprings. Where a single spring separates the two masses, there wouldappear to be substantially no difference in the point of fracture.Therefore, to develop a long throw for the actuator, I have found theuse of tandemly disposed springs, separated by an alignment plate, to beparticularly effective.

A further problem encountered in any attempt to utilize spring forcesfor service braking purposes, is that helical springs tend to impart anobjectionable twisting to the drive movement of the piston rod. Thistwisting can cause fracture of the rod if it is held fixed with aclevis. Furthermore, when several springs are used together, thistwisting causes buckling or scrambling of the springs thereby impairingproper functioning.

Accordingly, it becomes still further objects of the invention toprovide actuator devices for a brake system of the foregoing kind, inwhich these and other problems have been resolved.

These and other objects will be more readily apparent from the followingdescription of preferred embodiments when taken in conjunction with theaccompanying drawings, in which:

FIGURE 1 is a fragmentary perspective view showing the generalarrangement of a system suitable for employing an actuator according tothe invention, the system be ing shown in a typical environment, namelyin a truck or tractor member, illustrated in outline;

FIGURE 2 is a diagrammatic illustration of the brake system shown inFIGURE 1;

FIGURE 3 is a fragmentary View, partially in section of components ofthe system shown in FIGURE 1, shown in brake off position;

FIGURE 4 is a view comparable to that of FIGURE 3 but with thecomponents in a brake-set position;

FIGURE 5 shows diagrammatically another embodiment of a system suitablefor using an actuator according to the invention;

FIGURE 6 is a side elevation view partly in section of a brake actuator,according to the invention;

FIGURE 7 is a section view along the line 77 of FIGURE 6;

FIGURE 8 is an end view along the line 8-8 of FIG- URE 6;

FIGURE 9 is a section view along the line 99 of FIGURE 6;

FIGURE 10 shows the actuator of FIGURE 6 arranged to pull the brakelever to a brake set position;

FIGURE 11 shows another embodiment of a spring applied brake system;

FIGURE 12 shows a valve actuating means employed in the system of FIGURE11;

FIGURE 13 shows another embodiment of a valve actuating means as used inthe system shown in FIG- URE 11;

FIGURE 14 is a center-line section view of a brake actuating unitaccording to another embodiment;

FIGURE 15 is a section view taken along the lines 15-15 of FIGURE 14;

FIGURE 16 is an end view along a section at lines 1616;

FIGURE 17 is a section view of a portion of the actuator shown in FIGURE14 in its compressed condition;

FIGURE 18 shows a prior art valve construction;

FIGURE 19 shows another embodiment of a spring applied brake system;

FIGURE 20 schematically shows a simplified embodiment of a brakeactuating unit; and

FIGURE 21 schematically shows another simplified embodiment of a brakeactuating unit.

Ordinarily, in brake systems, as carried by wheel supported vehicleshaving an operators compartment, brake drums are provided including afriction surface. Co-acting brake shoes, carrying a friction lining, arearranged for movement into and out of engagement with the frictionsurface in order to apply and release the brakes. Not uncommonly, anoperating member, such as a lever arm, is movable between brake applyingand brake releasing positions in order to control the movement of thebrake shoes.

In general, brake actuating apparatus has herein been providedcomprising a connecting member operably connected to move the brakeshoes between brake applying and brake releasing positions. Theapparatus includes a cylinder, a piston within the cylinder, andresilient biasing means disposed to urge the piston with respect to thecylinder in order to advance a connecting member to apply the brakes forboth service and emergency operation. The apparatus has been simplifiedto the point where energy for advancing the connecting member duringboth service and emergency operation is derived substantially entirelyby releasing stored energy from the biasing means. Fluid pressure means,operable from the operators compartment, as by a foot pedal, is arrangedfor both gradually or substantially instantaneously releasing the storedenergy of the biasing means as well as to restore the energy thereof.

The apparatus as abovev described is adapted for either pneumatic orhydraulic operation. For example, hydraulic operation is shown inFIGURES 1 through 4 wherein the system is generally designated by thereference numeral 12. The system is preferably installed, for example,in a truck or tractor 13, as shown in outline in FIGURE 1. However, itsuse is equally of value to attendant members, such as a trailer, or inother vehicles which rely on wheels for support and on braking systemsfor control, such as aircraft.

Many types of hydraulic braking systems exist. All of such systems havein common, a hydraulic reservoir, an accumulator and a pump. The pump,being itself appropriately driven drives hydraulic fluid, underpressure, such as oil, to the various actuating members. In this respectthe instant system is no exception.

In other words, any existing or previously known hydraulic servicesystem which includes a pump, accumulator and reservoir 16, oftenlocated in the engine compartment, as in FIGURE 1, can be employed. Asis well known in the art, return lines to the reservoir, or sump, arerequired although such return lines are not shown in FIG- URE 1 forgreater clarity of disclosure.

The service pump drives fluid, under pressure, to a foot brake or cabcontrol valve 17. Conveniently, valve 17 is linked to the brake pedal 22and can be of rotary, fourway variety, with valve and seat dimensionssuch that the step of going from open to closed or closed to open is agradual rather than a substantially instantaneous one.

This is to say, that with the vehicle in normal cruising status (i.e.,in service operation), valve 17 is in a condition such thatsubstantially the full pressure exerted by pump 16 makes itself feltthrough the pump service line 18 and through valve 17 to the mainservice line 1 and thus, to the brake controlling cylinder 21. Whileimmediate full depression of brake pedal 22 is effective to cut off thepressure entirely and permit full, instantaneous flow-back through thereturn line to the reservoir, an intermediate or partial displacement ofthe brake pedal will elIect only a corresponding partial pressure lineblockage and opening of the return line, thus providing smooth partialbraking. Rotary valves capable of accomplishing this result are readilyavailable commercially and thus require, it is felt, no detaileddescription. Comparable remarks apply to certain other valvessubsequently described.

The main service line 19 leads into, and under customary conditions,through a stand-by or post-emergency valve 26 located adjacent cylinder21. While FIGURES 1 and 2 show only a single, main service line enteringstand-by valve 26, it will be realized, as stated above, that there isalso a separate return or feed-back line leading to the main pumpreservoir. This feed-back line is designated in FIGURES 3 and 4 by thereference numeral 19a.

Returning to line 19 (FIGURES 3 and 4) pressurized fluid in line 19 canmake its influence felt in the hydraulic pressure chamber 31, locatedadjacent the lefthand end of cylinder 21.

FIGURE 3 schematically represents a brake-off situation. Here, the fullpressure of line 19, through the normally fully open stand-by valve 26,is exerted through the fluid filled chamber 31 and against the pistonhead 33 of a plunger 34 projecting through and beyond the right-hand endof cylinder 21 and terminating in a clevis 36.

A helical spring 37, having a very powerful spring constant isinterposed between piston head 33 and the rod end 38 of cylinder 21 andserves to bias piston head 33 in a lefthand direction toward the headend 39 of the cylinder. Appropriate flanges 41 and 42 (FIGURES 3 and 4)assist in centering or maintaining spring 37 in proper axial alignment.

Under most circumstances, smooth operation of the main cylinder isenhanced by providing on the left.- hand end of cylinder 21 an eye-boltbracket 46 adapted to be pivotally mounted on an adjacent frame orchassis member (not shown) of the vehicle, thus enabling the cylinder torock slightly to conform to the requirements of the extensible andretractable plunger member 34. In this situation the fluid lines betweenvalve 26 and cylinder 21 would preferably be flexible to accommodate theslightly varying attitude of the cylinder.

Translation of plunger 34 and clevis 36 1s reflected in a reciprocating,or rocking movement, of a lever 51 pivotably mounted at one end onclevis 36 and secured at the other end to a conventional cam shaft 52 ofany standard vehicle brake mechanism, such mechanism being generallycharacterized by the reference numeral 56.

The brake mechanism, in known manner, is actuated or deactivated byangular rotation of cam shaft 52 (and cams 53) in one direction or theother. It is, therefore, not believed necessary to further describe thestructure and operation in detail except to state that a tension spring57 connected to brake shoes 58 tends to pull the shoes inwardly towardeach other about a pair of anchor pins 59 as a pivot, and thusdeactivate or release the brake by separating shoes 58 from theencompassing brake drum. As is known, the brake drum has a frictionsurface which co-acts with the friction lining carried by brake shoes58. Thus, when oppositely urged by earns 53, the brake shoes are movedto brake applying position whereby the linings engage the frictionsurface of the drums.

As appears most clearly in FIGURE 3, pressurized fluid from main serviceline 19 is, under customary cruising conditions, effective to urge thepiston in a right hand direction to overcome the leftward urging ofspring 37. As a consequence, spring 37 is compressed and plunger 34, camshaft 52 and the brake are in off position.

Should pressure in line 19 and chamber 31 drop, however, the urging ofspring 37 will drive the plunger to the left and overcome the force ofspring 57. Thus, the cam shaft is rotated in an opposite direction suchthat the brake will be in an on or set position. This situation couldoccur as a result of many different happenings, the most common,perhaps, being a breakdown of the hydraulic pump or a rupture or leak inthe feed hnes or valves.

Upon happening of such emergency, the brakes Will be set and the vehiclewill come to a halt. It is to be noted that while only one brakecylinder is shown in the figures, in actual practice a number ofcylinders will be employed for braking the several wheels of thevehicular equipment.

After the vehicle is stopped the operator may effect such repairs to thesystem as are possible. I have, therefore, provided a convenientstand-by or post-emergency system which is capable of restoring thecylinders and the attendant mechanism to operative condition.

This stand-by system, generally designated by the reference numeral 61includes a separate reservoir and pump 62 located in a convenientposition such as at one end of the drivers seat (not shown) in cab 60. Ahand operated lever 63 enables the operator to build up hydraulicpressure in pump 62 and, by suitable orientation of a valve handle 64,to transmit this pressure into a stand-by feed line 66 leading throughstand-by valve 26 and into chamber 31 of cylinder 21.

As is apparent, valve 64 controls the flow of fluid in both pressureline 66 and return line 66a.

Valve 26 serves a somewhat similar purpose in that suitable orientationof the cock 67 determines whether main service pressure and return lines19, 19a, respectively, on the one hand, or stand-by pressure and returnlines 66, 66a, respectively, on the other hand, shall be in operation.In other words, rotation of cook 67 cuts out lines 19, 19a at the timelines 66, 66a are cut in, and vice versa. Valve 26 is also capable ofturning off all lines in the event of cylinder failure.

Stand-by system 61 enables the operator to reactivate the braking systemand by pumping by hand, even While driving, he can maintain pressure anddrive the vehicle to a repair facility. Should it become necessary toset the brakes while driving under stand-by condition it is onlynecessary for the driver to reach down with his left hand and rotatevalve handle 64 until line 66a is placed in communication with the pumpreservoir. Under this condition, the biasing effect of spring 37 willurge piston head 33 in the lefthand direction .(FIGURES 3 and 4) andforce fluid outwardly through return line 66a. After braking has beeneffected, the driver turns handle 64 back to service position forcruising and pumps with handle 63 to restore pressure in cylinder 21 andthereby deactivate the brakes.

After the necessary repairs are made, the system is switched fromstand-by back to main service.

For run-away or comparable situations, I have provided, at a convenientlocation in cab an emergency or panic button 71 and an attendantquick-acting high volume bleed valve 72 located in lines 19. Valve 72 isactuated by a Bowden or push wire 73 leading from button 71. Uponoperating button 71, valve 72 immediately commences, and continues, toexhaust fluid to atmosphere, thus quickly dropping pressure in the lineand permitting all the actuating springs on all the brakes to set thebrakes quickly and fully. Concurrently, valve 72 cuts off further flowfrom pump 16.

Emergency valve 72 would be of special use where the driver determinesthat foot valve 17 is not sufficient under the circumstances.

As thus described, it will be readily evident that the foregoing systememploys in general a spring biasing means which stores substantially theentire energy for applying brakes in both service and emergencyoperation. As shown in FIGURES 5 through 10 a pneumatically operatedembodiment of the above sytem is described wherein pneumaticallyoperated fluid pressure means serve to control release of the storedenergy of the spring biasing means, as well as to restore such energy asis expended during braking.

The system, shown generally in FIGURE 5, includes fluid pressure meansoperable from the operators compartment for both gradually orsubstantially instantaneously releasing stored energy from the springbiasing means and for restoring the energy. An air pump or compressorunit 75 connects via line 76 and a check valve to discharge into an airtank 77 equipped with a conventional relief valve 78. Tank 77 leads vialine 79 to suitable valve means designated generally by the referencenumeral 80.

Means 80 serves to connect fluid pressure to brake cylinders or to ventair therefrom gradually or suddenly for both service and emergencyoperation. Valve means 80 (FIGURE 5), diagrammatically provides thevarious operations to control brake cylinders 90 and can, of course, beconstructed in any suitable manner.

Accordingly, a rotationally movable distribution member 81, responsiveto movement of a foot pedal (represented by movement of dashed line 82)carried in the cab of the vehicle, serves either to pressurize or ventthe brake cylinders to a selected pressure. Member 81 is formed with apassageway or channel 83 which makes connection between a line 84, whichtransfers air to and from cylinders 90, and one of several vent lines86.

' Between line 84 and member 81 a manifold 85 is provided to extendaround a substantial portion of the periphery of the member 81. A numberof vents designated 86a, 86b, 86c, etc., are distributed around thehousing of member 81 and extend generally radially therefrom. Each vent86 is provided with a pressure relief means such as units designated87a, 87b, 87c, etc., respectively. Each pressure relief unit 87 is setto relieve brake cylinder air pressure down to a predetermined level andhold the pressure at that level. For example, relief means 87a can beset to relieve air pressure exhausting via vent 86a to a level of p.s.i.Unit 87b can be set to establish a lower air pressure such as 110 p.s.i.In the condition shown, valve means 80 serves to connect compressor 75via line '79, channel 83, manifold 85 and line 84 to apply fluidpressure to brake cylinders 90. Clockwise rotation of member 81, on theother hand, serves to vent brake cylinder air pressure from line 84 viavia manifold 85 and channel 83 to any one of vents 86.

As noted above, braking forces for both service and emergency operationare applied at the wheels from the stored energy in the spring biasingmeans located in cylinders 90, whereby venting air from the cylinders 90releases the spring forces. These same spring forces will also actwhenever there is partial or complete failure of the air supply. Thedriver of the vehicle will notice a certain dragging on the brakes andbe led to effect repairs. Should failure of the air supply leave thebrakes fully applied, it may strand the vehicle in an awkwardcircumstance. Therefore, means for emergency release of the brakes havebeen provided.

Means for emergency application of the stored energy in the springbiasing means to move the brake shoes to brake applying position areprovided. Thus, if for any reason, venting of air pressure fromcylinders 90 via valve means 80 is ineffective to cause the springbiasing means to apply braking forces at the wheels, a panic button 192can be pulled. Button 192 is carried in the cab of the vehicle andserves to operate a three-way valve 193. Valve 193 is spring-loaded byspring 194 to a condition whereby line 191 normally leads to brakecylinders 90 via a manifold and manifold connection 195, 196respectively. Thus, normally, air is directed from manifold 195 to andfrom each of the vehicles brake cylinders 90 by means of piping 197connected to each. For emergency operation, valve 193 is provided with avent 198 exhausting to atmospheric pressure whereby pulling button 192serves via a Bowden wire connection 189 to move the spool 199 upwardlyto connect vent 198 to connection 196, thereby directly venting allbrake cylinders 90 quickly to atmospheric pressure.

For post-emergency release of the brakes, a cylinder 88 of compressedgas, such as air or carbon dioxide, is connected to a two-postion valve89 operated by a lever in the cab of the vehicle. Slight rotation ofvalve 89 serves to couple cylinder 88 to line 191 and at the same timeserves to disconnect line 84 from same. Accordingly, fluid pressure fromcylinder 88 serves to overcome the spring force and releases the brakeshoes.

In normal service operation, movement of foot pedal (82) serves torotate member 81 to interconnect line 84 via channel 83 to any one ofvents 86. Thus, slight clockwise rotation of member 81 serves to releaseair pressure in the brake cylinders 90' to less than full pressure so asto partially release the stored energy of the resilient biasing means.As this energy is partially released, the brakes are correspondinglyapplied. Further, clockwise rotation of member 81 serves to connectsubsequent vents 86 to drop the air pressure in cylinders 9th as desiredfor commensurately increased braking. Release of foot pedal (82) servesto return member 81 to the position shown in FIGURE under the urging ofany suitable resilient means (not shown). While means 80 is shown asoperating by discrete steps, any suitable variable relief means can beemployed therefor.

A system employing a fluid pressure signal to control reservoirpressures which in turn develop the forces to operate the brakes isshown schematically in FIGURE 11 as adapted for pneumatic operation, thefluid being compressed air.

The signal air system of FIGURE 11 comprises generally a source of fluidunder pressure represented by the arrow 13%. A first valve means 14% isdisposed between the source of fluid pressure and the brake cylinders ofthe above type wherein spring forces are employed to urge a brake shoeinto brake applying position. The first valve means is operable in onecondition to transmit a fluid pressure into the brake cylinders todevelop a force suflicient to overpower the spring biasing means in thebrake cylinder. In another condition the first valve means 1% serves tovent fluid pressure from the brake cylinders to release stored energy ofthe spring biasing means.

In order to closely control operation of the first valve means invarying degree between the first and second condition mentioned above,an actuator 160 is provided which is responsive to, and disposed by, abiasing fluid pressure acting normally to fully condition valve means149 to its brake releasing condition. A counteracting fluid pressurewhich can be varied is introduced to the actuator to operate valve means148 in varying degree to its brake applying condition. Another valvemeans 240 is provided which is operable from the operators compartmentof the vehicle for both gradually and substantially instantaneouslyvarying and directing fluid pressure from source to the actuator tooperate the actuator in a corresponding varying degree.

In short, a limited depression of valve means 241 generates a relatedlimited fluid pressure signal which serves to correspondingly reducepressure in the brake cylinders whereby the energy stored in the brakesprings is partially released.

In general, operation of the system shown in FIGURE 11 proceeds asfollows. Fluid pressure from source 130 is applied to a service line131. Fluid pressure is carried along one branch 132 through a parkingand emergency brake control valve 133 described further below. Pressurefrom branch 132 is applied to yieldingly urge or bias the actuator 16!)in a downward direction and also supplies a predetermined pressure to anair receiver tank 134. Tank 134 is protected against any sudden drop inpressure by a chack valve 135 on the inlet side. The outlet 136 of tank134 supplies fluid under pressure to the inlet port 137 of valve meanscontrolled by actuator 160. Under the normal biasing action of thepressure applied to actuator via line 138 valve means 140 is conditionedto pass fluid under pressure from inlet 137 to outlet 139 andsubsequently to the brake cylinder via line 197'. This fluid underpressure serves to move the piston of the brake cylinder to brakereleasing position.

Means serving to control application of the brakes includes afoot-operated valve means 246 for developing a fluid pressure signal inline 141 to be applied through an inlet 142 whereby the biasing forcedeveloped by pressure in line 138 can be partially or fully overcome.

A foot pedal operated valve of known design, such as theBendix-Westinghouse Corporations Model E2 construction shown in FIGURE18, can be used to provide a controlled air pressure serving as a fluidpressure signal.

When the brake pedal 200 (FIGURE 18) is pressed down by the driversfoot, force is exerted on the piunger 201, rubber graduating spring 202and to the piston assembly 203. Vertical movement of assembly 203 servesto modulate or vary the source pressure so as to supply and maintain aselected brake signal air pressure. The signal air pressure can then bedirected to control the venting of pressure in the brake acuator units.As the piston assembly 203 moves down, its stem including an exhaustseat 204 closes the exhaust, which is otherwise normally open. As theexhaust closes, the inlet valve 285 moves off its seat. Air pressurefrom the reservoir then enters gradually via inlet valve 265 and flowsout at a selected pressure via delivery ports 296 to supply an airpressure signal to the system.

Assuming a given downward displacement of plunger 261, the signal airwill develop and maintain a corresponding pressure. When the airpressure in the cavity beneath the piston and the air pressure which isbeing delivered via ports 2&6 equals the mechanical force depressingplunger Ztil, the piston lifts to close off further incoming air. Theexhaust remains closed to prevent loss of the signal pressureestablished.

Thus, the valve seeks a balanced condition where pressure beneath theassembly 203 equals the effort exerted by the drivers foot. Maximumdepression of plunger 201 serves to maintain the inlet valve fully opento deliver reservoir pressure.

If pedal 200 is released, the air pressure beneath the piston assembly233 moves it upwardly to fully open the exhaust. Air below pistonassembly 203 and in lines connected to ports 206 drops accordingly toatmospheric through the exhaust port.

Further explanation of the known valve construction shown in FIGURE 18is not considered necessary. Identification of certain other elementsmay, however, be helpful. Thus, the construction includes a roller 2119,retainer 210 for rubber spring 2132, boot 211, return spring 212, spring213, exhaust diaphragm 214, and a piston retainer cap 215.

Valve means 149 can be of similar construction to valve means 24!)described above whereby downward movement of a plunger in varying degreeserves to pass a proportionate pressure through the valve.

One embodiment of the valve actuator 160, and its relationship to avalve means 140, such as the Bendix- Westinghouse Corporations Model E2construction described above, is shown in FIGURE 12. Generally, theactuator includes a plunger arranged, whereby under pres sure of thefluid source the plunger normally serves to condition valve means 140 tomaintain the spring means of the brake cylinder in its fully restoredcondition. An inlet for applying to the plunger a counteracting fluidsignal pressure is provided, either to partially or fully release storedenergy of the brake springs, depending upon the degree of operation offoot pedal 200. Thus, the varying degree of signal pressure developed atthe inlet correspondingly releases the stored energy of the brake springmeans.

In the embodiment in FIGURE 12 the plunger means is arranged to comprisefirst and second expansible pres sure chambers, each having a movablewall. The walls are of different pressure-receiving areas and aremovable as a unitary construction between advanced and retractedpositions. The pressure-receiving area of the movable wall of the firstchamber is less than of the second chamber. A plunger actuator member orconnecting rod is movable with the walls. Fluid passage means areprovided normally passing fluid pressure from the pressure source intothe first fluid pressure chamber to urge the movable walls and the valveactuator member to its advanced position. The inlet for applying acounteracting fluid signal pressure is disposed to pass fluid pressureinto the second expansible chamber under control of valve means 240 tourge the movable walls toward their retracted position.

Particularly, an expansible pressure chamber 145 is defined by thecylinder 143 and piston head 144 movable therein. A second expansiblechamber 146 is defined by a cylinder 147 and piston head 148. Heads 144and 148 are held in fixed spaced relation by an axial rod portion 149.The pressure-receiving face 151 of head 144 provides apressure-receiving area smaller than the pressure receiving face 152 ofhead 148. Accordingly, with equal pressure applied to faces 151 and 152,the piston head construction will be moved upwardly to a retractedposition defined by an annular shoulder 153 provided by the cylinderblock 154. Cylinder block 155 is bolted to block 154 and, if desired,suitable sealing gaskets can be provided therebetween, if considerationis properly given to variation of the stroke of member 156.

Plunger actuator member 156 is screwed axially into the piston headassembly and carried between advanced and retracted positions thereof.At the bottom end of member 156 a cylindrically shaped cup 157 isdisposed to contact and depress plunger 2111 of valve means 140described above. As previously explained, downward depression of plunger201 serves to transmit fluid pressure from inlet 137 (FIGURE 11) tooutlet 139, thereby moving the brake pistons to brake releasingcondition. During movement of the piston head assembly between advancedand retracted positions, it will be observed that the volume of the deadair space defined between piston head 144 and piston head 148 willcorrespondingly increase or decrease depending upon the direction ofmovement of the head assembly. A fluid vent 158, bored through cylinderblock 154 and terminating in shoulder 153, is disposed to providebreathing for this dead air space. Furthermore, vent 158 serves toprovide access for lubrication of piston heads 144, 148 on the lowpressure side of each.

A fluid signal pressure inlet 142 (FIGURE 11) serves to inject acounteracting fluid pressure into chamber 146 to partially or fullyovercome a biasing force developed by pressure injected into chamber vialine 138. Memher 156 can therefore be moved in varying degree to aselected position to control the fluid pressure at outlet port 139.

Another embodiment of the valve actuator is shown in FIGURE 13 whereinthe expansible walls are provided by resilient deformable diaphragms161, 162 each sealed at its periphery to the wall of its respectiveexpansible chamber 163, 164. Chambers 163, 164 are respectively providedby a cylinder block 165, a cylinder block 166 and an intermediatecylinder section 167. Section 167 is formed with a pair of openings 168,169 bored from opposite faces to provide sealing surfaces to support theback side of each diaphragm 161, 162 and permit flexing thereof.Accordingly, the back surface of each diaphragm is supported around acircumference corresponding to that of its chamber 163, 164. A stem 171is carried by diaphragms 161, 162 and movable therewith by means of thehexagonal nuts and washers shown. Accordingly application of a fluidbias pressure, via line 138, serves to drive stern 171 downwardly to theadvanced position whereas application of a counteracting pressure viainlet 142 serves to provide a counteracting force to move stern 171 inan opposite direction thereby applying the brakes.

Valve means 133 serves to provide a parking and emergency brake functioncontrolled manually from the cab of the vehicle or automatically inresponse to a pressure drop in the fluid pressure source.

It should be noted that a spring is disposed in valve means 140 to urgeplunger 201 (FIGURE 18) upwardly when pressure is relieved from line 138at times when no counteracting pressure is applied via inlet 142.

In general, a large capacity valve 133 is disposed upstream of actuatormeans 160. Valve 133 is positionable whereby in one condition, ittransmits a biasing fluid pressure to the actuator. Valve 133, whenmoved from the position shown in FIGURE '11 serves to quickly relievethe biasing pressure through a vent 172 leading to a low pressure areasuch as the outside surroundings. Accordingly, venting bias pressurefrom line 138 by means of valve 133 serves to permit the spring in valvemeans 140 to move plunger 201 (FIGURE 18) and actuator means upwardly toits brake applying position.

In order to release the brakes, it is necessary to reapply a downwardforce to actuator means 160. This release movement depends uponprovision of a source of fluid under pressure in line 138. Spools 290,291 of valve 133, when moved to the left as shown in FIGURE 11, connectlines 172 and 138 to vent the bias pressure from valve actuator 160causing brakes to be applied. Manual control by pulling out the parkingknob 292, vents the bias line 138. Service system pressure in line 132normally serves to restrain spring 293 by a force developed via bleedline 294. When knob 292 is pulled to the park position, 295, pressurefrom line 132 cannot enter the valve housing 296 and, therefore, spring293 serves to keep the valve in its park position.

As a pressure sensing means, spring 293 serves to overcome unusually lowpressure in line 132 to apply the brakes by venting the line 138. Manualreset is subse- 1 1 quently required so as to impart an additionalsafety factor to its operation.

Another fluid pressure signal type system employing an actuator meanscontrolled by receipt of fluid pressure signals and operating tocounteract a bias pressure to release stored energy of springs in abraking system is shown in FIGURE 19. The system in FIGURE 19 includes afluid pressure source including a compressor 173 supplying fluid underpressure to a reservoir 174 through a check valve 175. A recirculatingline 176 incorporating a governor 177 provides a return to compressor173. A fluid shutoff means 178 is provided by a pet cock in an outputline 179 leading from reservoir 174. When shutoff means 178 is disposedto disconnect reservoir 174 from primary service system elementsdownstream thereof a standby emergency system for limited operation ofthe brakes can be activated.

The emergency standby system generally includes a spare fluid pressurereservoir 180 protected by a check valve so as to form a second sourceof fluid under pressure when used in combination with compressor 173 andreservoir 174 or, in the event of the failure of either of the latter,can be used by itself for a limited period. Thus, when compressor 173and reservoir 174- are fully operative, compressor 173 will serve tomaintain pressure in reservoir 180 at a predetermined level viareservoir 174. Where so called wet and dry tanks are required in orderto comply with motor vehicle regulations or physical system performance,reservoirs 174, 180 can be employed to meet this requirement. Thestandby system further includes a hand-operated valve 181 connected tovary and transmit pressure from reservoir 180 directly to the brakecylinders so as to release the brakes in a corresponding degreedependent upon manipulation of valve 181. Valve means 140 or 240 canserve this purpose when modified for hand control as by employing a handlever rotating a camming portion to move plunger 201 (FIG- URE 18) asdesired. A closed center three-way valve 182 is disposed immediatelyupstream of each brake cylinder whereby the fluid pressure line 183, canbe selectively connected or disconnected to control the brake cylinder.Valve 182 can also be conditioned to selectively connect and disconnectthe primary service brake system when in position identified by theletter s, as well as being able to be disposed to disconnect the brakecylinder entirely from both systems.

Operation of the primary service system of the arrangement in FIGURE 19follows substantially along the lines of the system previously describedwith respect to FIG- URE l1 and accordingly it is not considerednecessary to repeat that description at this time.

As noted above, emergency braking has been effected in the past, bymeans of spring forces which are released upon failure of the airsystem. I have observed that while these springs have been sufiicient toserve as parking brakes, their operation has been of such limitedeffectiveness that in a number of jurisdictions it has even becomeunlawful to refer to them as emergency brakes. I have further observedthat their effectiveness is reduced by reason of requiring them toremain compressed over long periods of time, extending for example, intodays and weeks. Furthermore, the flexing life of single large sizedsprings as used in many emergency braking systems is relatively short.

Accordingly, I have provided preferred braking means as now to bedescribed which can be operated either bydraulically or pneumatically ineach of the above described systems, and which will provide satisfactoryoperation over an extended period relative to the life of the vehicleitself.

In general, the brake cylinders as designated by the reference numeral90 (FIGURES 5 and each include a cylinder, a piston movable within thecylinder, and a connecting member carried by the piston for moving thebrake shoes between brake-applying and brake-releasing 12 positions.Resilient biasing means are provided to yieldingly urge the piston withrespect to the cylinder to move the connecting member.

The resilient biasing means preferably comprises a number of helicalsprings, each having an axis spaced from the axis of the cylinder andextending substantially parallel to the cylinder axis. The axes of thesprings are spaced from each other and distributed around the cylinderaxis, thereby providing a long-lived and powerful spring biasin means. Afluid receiving space is defined between one end of the cylinder and thepiston and adapted to be pressurized either by hydraulic fluid or bypneumatic means to overcome the urging of the powerful resilient biasingmeans. In a particularly preferred embodiment, plural banks of short,lightweight helical springs are provided Within the cylinder andseparated by a plate which is mutually supported by the adjacent banks.Thus, the banks are arranged in tandem generally axially of thecylinder. Should any one of the springs become defective, it will havevirtually no harmful effect upon the overall braking efiiciency of thecylinder.

In particular, a cylinder is provided with an end cap member 92 formedwith an annular skirt 93. Skirt 93 is adapted to extend coaxially intocylinder 90 and is welded at 94 to form a sealed closure. The innersurface of member 92 is formed to include a number of cylindrical seats95 adapted to receive helical springs 96 therein.

At the other end of cylinder 90 a movable piston 97 is carried to rideon a pair of relatively widely spaced 0- rings 98a, 98b, disposed aroundthe axially extending skirt 99 of piston 97. The relatively wide axialspacing between O-rings 98a, 98b, serves to prevent binding of piston 97within cylinder 90. The end surface inside piston 97 is formed toprovide circular seats 101 substantially aligned with correspondingseats 95. Springs 96, in the main, are distributed substantiallyparallel to and spaced from the axis of cylinder 90 as well as beingspaced from each other. Two of the springs 96 are disposed coaxially ofcylinder 90 and positioned in tandem. The ends of springs 96 are carriedin seats 95, 101 and can (in another embod'unent) extend continuouslyfrom one end to the other. However, the arrangement employing arelatively large number of springs arranged in two tandem banksextending along the axis of cylinder 90 is preferred. As noted, the twobanks are separated by a plate 102 mutually supported by the springs ofboth banks.

Plate 102 is formed with oppositely extending boss portions 103, 104.Portions 103, 104 fit within an end convolution of the springs to carrythem respectively between boss portions 103, 104 and seats 95, 101. Acylindrically shaped opening 105 extends through plate 102 coaxially ofeach pair of boss portions 103, 104. With the exception of that opening105 disposed coaxia-lly of cylinder 90, openings 105 serve to receivecylindrical guide members 106 which are carried substantially coaxiallywithin springs 96 and mounted in seats 95. The peripheral edge of plate102 carries an O-ring 107 to take up any abrasive wear which mightotherwise be encountered by springs 96. Guide cylinders 106 arepreferred mostly for use with long springs extending end to end incylinder 90 when not employing plate 102. Thus, as shown, plate 102 can,if desired, be removed and longer springs be employed.

In order to reject moisture which might otherwise tend to accumulatewithin cylinder 90, when used as a pneumatic system, the cylindricalspace defined between the irmer surface of member 92 and of piston 97includes a free volume of water-rejecting lubricant, such as motor oil.It is preferred for most purposes that the amount of this free volume ofoil be on the order of a quart as distinguished from slight deposits asmight be used for mere lubrication. In the embodiment shown in FIGURE 6,means for passing the motor oil into cylinder 90 include 13 a fillingcap 307 screwed onto an exteriorly threaded boss 120.

Means for sealing, substantially moisture-free the space defined betweenmember 92 and piston 97 from the space 100 defined between the pistonhead and the adjacent end of cylinder 90 includes, in addition to thepair of spaced O-rings 93a, 98b, an encircling wick 108 of suitableabsorbent material such as felt, carried in wiping engagement with theside wall of cylinder 90. Wick 108 is disposed near the trailing edge ofskirt 99 so as to be interposed between the moisture-free space andO-ring 98b. Plate 102 includes fluid transfer holes 1021: to insure freemovement of the oil thereacross, from one side to the other.

Piston 97, as shown in FIGURE 6, is in fully extended position. Thiscondition normally will not exist while the cylinder is mounted on thevehicle but rather is representative of the condition of piston 97 priorto installation. In this condition, the head of piston 97 abuts the endof cylinder 90. Fluid passage means for pressurizing and latercontrolling piston 97 against the urging of springs 96 includes therelatively large port 109. Port 109, being relatively large, is notsubject to becoming clogged with grit, dirt and the like as has been acommon source of air brake problems.

Prior to installation, port 109 is connected to the compressed airsupply whereby space 100 can be subjected to pressure. In order toprovide sufiicient active pressurereceiving area to enable installationto be made, means are provided for injecting fluid under pressure,between the end surface of piston 97 and the abutting end of cylinder90. Thus the end surface of piston 97 includes a plurality of radiallyextending depressions 110 providing sufficient pressure-receiving areain fluid communication with port 109 whereby sufficient force isgenerated to overcome the spring biasing means. With the pistonpartially retracted under fluid pressure, cylinders 90 can be connectedup and mounted to the vehicle.

As shown in FIGURE 5, the brake shoes 117 are arranged to be moved to abrake set position by clockwise rotation of lever arm 116. A connectingmember or rod 112 can be threadedly engaged in the end of piston 97 andconnected at its other end in the system as shown'in FIGURE 5. It shouldbe noted that in FIGURES and 6, rod 112 is arranged whereby movement tothe right, i.e., pushing on rod 112, serves to move the brake shoes tobrake-applying position. In this instance cylinder 90 can be mounted bystuds 111. Rod 112 extends through an exteriorly threaded boss 121 whichin turn carries a removable gland member 122 provided with a pair ofO-rings 123 and wiper 124.

Where it is desired to move the brake shoes to brake applying positionby pulling on rod 112, rather than by a pushing action, rod 112 can bereadily removed and passed through the opposite end of cylinder 90 viaboss 120 until it engages threads 113 in piston 97. In the latter event,cylinder 90 can be carried on the vehicle by means of a pair of radiallyspaced brackets 114 (FIGURE 8). When brackets 114 are used to mountcylinder 90, the double-pivoted clevis 115 (FIGURE 5) can be replaced bya single connecting pin inasmuch as brackets 114 serve to permitcylinder 90 to rock slightly to compensate for the arc defined by theupper end of lever arm 116. In the pulling arrangement (FIGURE 10), boss120 serves as a filling opening to permit moisture rejecting oil to besupplied to cylinder 90, prior to insertion of rod 112.

From the foregoing description, it will be evident that failure orfatigue of any of springs 96 is easily compensated by means of plate102. At the same time, a powerful spring force is provided while takingadvantage of the longer flexing life of short, lightweight springs whichcan be on the order of conventional automotive valve springs.

As shown in FIGURE 10, piston 97 moves to an intermediate position incylinder 90 when the brake shoes are fully applied. It will be evidentfrom the spacing between the piston head and the adjacent end ofcylinder that considerable throw is left in reserve. Thus, if the brakelinings are entirely destroyed, the brake shoes can nevertheless befurther driven if need be, even into metal-to-metal contact with thedrums after destruction of the linings whereby the shoes and drum willfuse under heat generated thereby. With this reserve throw, the problemof fading is virtually eliminated.

While the throw of member 112 is considerably increased, the over-allextent of cylinder 90 remains as short or shorter than conventionalunits.

If it is desired to operate without benefit of plate 102 helical springssufficiently long to extend from member 92 to the inner surface ofpiston 97 can replace the tandem pairs of shorter springs shown. In thisevent, cylindrical guides 106 serve to maintain the springs in analigned condition whereby the springs do not interfere with one anotheror with the operation of piston 97.

As noted above, a commercially acceptable brake unit for the abovesystems must provide the flexing qualities characteristic of low forcesprings while developing a satisfactory spring force to actuate thebrakes. This must be achieved, however, while avoiding the adversebuckling and cocking normally encountered at those convolutions locatedrespectively either midway between, or at the ends of the spring. Itwill also be recalled that the compression spring means used shouldprovide a sufficiently long stroke to eliminate the fading problemwithout significantly extending the length of the brake cylinder unitbeyond conventional lengths.

In providing spring biasing forces suflicient to be employed in servicebraking operation of a vehicle, such as a heavily laden tractor-trailerrig, spring life is obviously important. It is generally considered thatcompression springs, for best results, should be limited to a maximumflexure of half their length for springs having a length three timestheir coil diameter. Thus, for a spring of twoinch coil diameter apreferred length (3:1) of six inches should not be compressed in normaloperation much more than three inches. Therefore, as shown above, sevensprings of roughly two-inch coil diameter are arranged in a single bankto generate suflicient braking force at the wheels. A second, andsimilar bank of springs is added to develop a preferred rather extendedthrow of the piston.

At this point, if additional spring force is to be developed, morepowerful springs or additional springs can be used. The former will losesome of the flexing advantage of lower power springs, while the latterwill either require an increased brake cylinder diameter or use ofsprings of a smaller coil diameter. If the springs are to be of equallength of the seven two-inch diameter springs shown, their diminishedcoil diameter will violate the rule of diameter to length stated abovefor preferred performance.

I have observed, however, that if the axis of these smaller diametersprings is closely confined during flexure whereby lateral movement ofthe axis is restrained, the 3:1 preferred relationship can bedisregarded without adverse effect. I have further observed that as theratio of length to coil diameter increases, the wire diameter of thespring normally will be decreased to provide further improved flexinglife. Thus, in a particularly preferred embodiment (FIGURE 14) describedbelow, I have employed a nested helical spring construction wherein aplurality of three helical springs are concentrically disposed, theouter spring having substantially the optimum 3:1 relation of length tocoil diameter. The outer spring employs a helix of opposite hand to thenext adjacent inner spring and this scheme has been found to provideexcellent lateral restraint such as when a close spaced sliding fitrelation on the order of .010 inch is employed. The free volume of oilwithin the cylinder provides spring lubrication.

To further preclude lateral movement of the spring axis, a guide post istelescopically carried axially of the nested springs and supported fromthe divider plate. The divider plate serves, as above, to permit theaxial displacement of the brake piston to be effectively doubled withoutdetriment, such as fracture of the springs midway between the sprung andunsprun g masses.

The divider plate, while supported by the helical spring arrangement oneach side, is formed slightly spaced from the side wall of the cylinderto accommodate any limited tilting movement thereof caused by failure ofone of the springs. At one end of the springs, the guide posts areformed with a tapered enlargement of their diameter to provide an axialseat within an end convolution of the innermost spring. A coaxialannular seat encircles the end convolution of the outermost spring. Atthe other end of the nested springs, an annular recessed surface andperipheral rim form a seat while a circular boss protrudes coaxiallywithin the innermost spring.

The guide posts are suiliciently elongated whereby, upon maximum springcompression, they will extend axially of the springs to within a slightspaced relation with respect to the boss aligned therewith therebyensuring that the end convolutions of the springs do not become unseatedor cocked at an angle as can be caused by the twist generated in springcompression movement.

The skirts of the piston and cylinder end-cap, and the outer margin ofthe divider plate meet when the piston is at its full spring compressionposition so as to define the maximum spring compression relation, andevenly relate the load between each bank, while precluding coil contact.

The arrangement as described in general above is shown in detail in theembodiment of FIGURES 14 through 17.

A brake cylinder 250 is formed with a relatively thick end portion 251to accommodate a rather large diameter fluid passage 252 for admittingfluid under pressure into the interior of cylinder 250. The other end ofcylinder 250 is, as formed, open. To seal the open end of cylinder 250an end cap 253 is welded at 254. Cap 253 is provided with a skirt 255 ofequal axial extent to a skirt 256 of a movable piston 257. Piston 257 isformed with a piston rod 258 for connection to a brake actuating camlever such as shown at 116 in the system in FIGURE 5. In order tosupport the brake unit in its installed position, a pair of mountingstuds 259 (only the far one of which is shown) are formed to protrudefrom end portion 251 on opposite sides of piston rod 258.

In order to provide breathing for that portion of the interior ofcylinder 250 that is defined between skirts 255 and 256, a fluid passagefitting 261 is provided coaxially of end cap 253. As noted above, theinterior of cylinder 250 carries a small deposit of water-repellantlubricant and this lubricant can therefore, be injected into thecylinder via fitting 261.

The divider plate 262 is formed at its periphery to receive an O-ringwhereby plate 262 moves axially along the cylinder with a loose fit, onthe order of a sixteenth inch radial clearance to accommodate a slighttilt if a spring should fail. Plate 262 carries a plurality of guideposts 263 of preferably solid construction from end to end. Posts 263are formed at their midpoint with a tapered enlargement 264 of theirdiameters to snugly receive the end convolution of the innermost helicalspring 265.

A nested arrangement of three springs 265, 266 and 267 is slidablysupported around each of the seven guide posts 263. In the drawings, forsake of clarity and simplicity of illustration, only a pair of nestedtandernly aligned springs so arranged has been shown. The helix of theinnermost and outermost springs, respectively 265, 267, is of the samehand whereas the helix of spring 266 is of an opposite hand wherebyentanglement of adjacent springs is precluded and smooth sleeve-likeguidance of each spring achieved. The coils of springs 265- 16 267 areradially spaced from one another to provide a slight sliding clearanceon the order of .010 inch, thereby restraining lateral movement of theircommon axis. The free volume of lubricant in the cylinder aids relativeaxial movement therebetween.

At the ends of the outermost springs 2&7 located remote from plate 262an annular seat is provided to encircle the end convolution of thespring to ensure that the end convolution of the springs will not becomeunseated or cocked at an angle under the twisting movement generated byspring compression. Thus the annular seat includes a protruding boss 268axially aligned with its respective guide post 263. A recessed annularsurface 269 encircles boss 268 and the outer periphery of surface 269 isformed to include an axially extending rim portion 270.

Guide posts 263 are sufiiciently elongated whereby upon maximum springcompression, as defined by abutment between skirts 255, 256 with theperipheral margin of plate 262, a slight spacing 271 (FIGURE 17) servesto prevent the springs from becoming unseated during operation of thebrake cylinder. Spacing 271 can preferably be on the order of one or twothicknesses or less of the wire diameter of the innermost spring.

Divider plate 262 is further provided with fluid passages or ports 272(FIGURE 16) for equalizing the transfer of fluid between each side ofplate 262.

As shown in FIGURE 14 the piston head 257 is adapted to abut the innerend surface of cylinder 250. This condition, while normally not existingduring operation of the brake unit, will exist prior to installation ofthe brake unit on a vehicle. Accordingly, at the time of installation itwill be necessary to inject fluid pressure between the inner end ofcylinder 250 and piston 257. The pressure must be sufficient to developa force which will overcome the biasing force of the springs within thecylinder. The pressure-receiving surface of piston 257 which is adaptedto abut the inner end of cylinder 250 is there fore formed (FIGURE 15)to include alternately raised and relieved areas closely spaced touniformly distribute the loading of the spring biasing forces actingagainst the piston head from the other side when the head is in itsabutting condition.

Uniform distribution of these spring forces generally across the entireface of piston 257 is necessary to prevent cracking or distortion of thepiston head, as will be readily apparent when it is considered thatsomewhere on the order of 4200 pounds of force is developed by springsemployed in the embodiment shown in FIGURE 14.

This force can be developed using a spring 267 developing 300 pounds offorce, a spring 266 developing 200 pounds of force, and a spring 265developing pounds of force. The spacing and extent of the surface areasprovided by raised portions 274 must not, however, preempt the provisionof a sufliciently large pressure receiving area formed by the recessedportions 275 which are in fluid communication with the fluid passage 252so as to receive fluid pressure and develop a force which can overpowerthe force of the spring biasing means. Accordingly, the arrangementshown in FIGURE 15 has proven satisfactory for accommodating both of theforegoing requirements.

Simpler embodiments of the above construction are shown in FIGURES 20and 21. In FIGURE 20, for example, there is shown a brake unit of theabove described kind wherein spring forces are employed to drive apiston to brake applying position which includes a plurality of helicalsprings 280, 281 disposed in concentric closely spaced relation, whereinthe helices of the adjacent springs are of opposite hand to each otherand the spaced relation between the springs measured radially thereof issufficiently close whereby the outer spring serves to guide and confinethe adjacent spring movement substantially to axial movement thereof. Itwill also be observed that posts 282, 283 are axially ali ned coaxiallyof springs 17 280, 281 and are elongated to provide a close spacedrelation at their ends. Vent 284 provides breathing.

As shown in the embodiment of FIGURE 21 a brake cylinder unit ofsimplified construction includes a single helical spring 285 having apowerful spring constant and a guiding divider plate. Thus, helicalspring means act axially of the cylinder and are disposed aroundcylindrically shaped guide means 286 extending a substantial distancealong the cylinder concentrically of and closely spaced from the helicalsprings 285 so as to slidably confine the axis of springs 285 andsubstantially preclude lateral movement thereof during longitudinalmovement of the piston 287.

From the foregoing it will be evident that a system of the above kind,made commercially feasible by the actuating units described, will have anumber of operating advantages as previously noted.

I claim:

1. Brake actuating apparatus comprising a connecting member adapted tobe moved to operate a brake shoe between brake applying and brakereleasing positions, a cylinder, a piston movable within the cylinder tomove the member, spring biasing means providing a source of storedenergy to drive said member to brake applying position, said biasingmeans including at least two banks of helical springs within saidcylinder and disposed to move said piston in brake applying direction, aplate separating said banks and mutually supported by both, each bankincluding a plurality of springs, each having an axis extendingsubstantially parallel to the cylinder axis, the axes of the springsbeing spaced from each other and distributed around the cylinder axis,and a fluid receiving space defined between one end of the cylinder andthe piston and adapted to be pressurized to overcome the urging of saidspring biasing means.

2. Brake apparatus as defined in claim 1 wherein said fluid receivingspace is adapted to be pressurized by pneumatic means, and furtherincluding another fluid receiving space defined between the other end ofsaid cylinder and said piston adapted to receive a free volume ofwaterrejecting lubricant in same.

3. Brake actuating apparatus according to claim 1 wherein the peripheryof said plate moves slidably along the inner wall of said cylinder andincludes fluid transfer openings throughout.

4. Brake apparatus as defined in claim 2 further including means forsealing the last named space substantially moisture-free from the firstnamed space, the last named means comprising a pair of spaced O-ringssupporting said piston within said cylinder, and an encircling absorbentwick carried by said piston in wiping engagement with the side wall ofthe cylinder, the axial disposition of said wick being between said lastnamed space and said O-rings.

5. Brake apparatus as defined in claim 4 wherein said lubricant is oiland said wick is formed of felt.

6. Brake actuating apparatus comprising a connecting member adapted tobe moved to operate a brake shoe between brake applying and brakereleasing positions, a cylinder, a piston movable within the cylinder tomove the member, spring biasing means providing a source of storedenergy disposed to drive said member to brake applying position, saidbiasing means including first and second right cylindrical helicalspring means tandemly disposed in said cylinder and of substantiallyequal force, a rigid, movable plate assembly extending transversely in asingle plane and slidably engaging the wall of said cylinder andseparating said first and second helical spring means and mutuallycarried along said cylinder by both said spring means, and a fluidreceiving space defined between one end of the cylinder and the pistonadapted to be pressurized to overcome the urging of said spring biasingmeans, an elongated cylindrically shaped guide member carried by theplate to extend along said cylinder and disposed snugly coaxially withinsaid helical springs to confine the axis of said springs andsubstantially preclude lateral movement of said axis during longitudinalmovement of the piston.

7. Brake actuating apparatus comprising a connecting member adapted tobe moved to operate a brake shoe between brake applying and brakereleasing positions, a cylinder, a piston movable within the cylinder tomove the member, spring biasing means providing a source of storedenergy disposed to drive said member to brake applying position, saidbiasing means including first and second helical spring means tandemlydisposed in said cylinder, a rigid plate assembly extending transverselyin a single plane and separating said first and second helical springmeans and mutually supported by both, the outer edge of said plateassembly slidingly engaging the wall of the cylinder, said helicalspring means on each side of said plate assembly including a pluralityof helical springs disposed concentrically of one another, the helicesof adjacent springs being of opposite hand, and a fluid receiving spaceddefined between one end of the cylinder and the piston adapted to bepressurized to overcome the urging of said spring biasing means, saidplate assembly including fluid passages therethrough for freelytransmitting fluid from one side to the other.

8. Brake actuating apparatus comprising a connecting member adapted tobe moved to operate a brake shoe between brake applying and brakereleasing positions, a cylinder, a piston movable within the cylinder tomove the member, spring biasing means providing a source of storedenergy disposed to drive said member to brake applying position, saidbiasing means including first and second helical spring means tandemlydisposed in said cylinder, a plate separating said first and secondhelical spring means and mutually supported by both, a fluid receivingspace defined between one end of the cylinder and the piston adapted tobe pressurized to overcome the urging of said spring biasing means,elongated cylindrically shaped rigid guide posts carried by said plateto extend substantially normal thereto and coaxially disposed Withineach of said springs to confine the axis of the latter to substantiallypreclude lateral movement of said axis during longitudinal movement ofthe piston, said guide posts being tapered to enlarge their diameter andform an axial seat within an end convolution of the springs.

9. Brake actuating apparatus comprising a connecting member adapted tobe moved to operate a brake shoe between brake applying and brakereleasing positions, a cylinder, a piston movable within the cylinder tomove the member, spring biasing means providing a source of storedenergy disposed to drive said member to brake applying position, saidbiasing means including first and second helical spring means tandemlydisposed in said cylinder, a plate separating said first and secondhelical spring means and mutually supported by both, said helical springmeans on each side of said plate including a plurality of helicalsprings disposed concentrically of one another, the helices of adjacentsprings being of opposite hand, and a fluid receiving space definedbetween one end of the cylinder and the piston adapted to be pressurizedto overcome the urging of said spring biasing means, said piston and theend of said cylinder each being formed with annular recessed seatsdimensioned to receive the end convolution of the outermost one of saidconcentric springs, said seats being further formed to include a raisedannular alignment boss disposed concentrically of and snugly receivedwithin the innermost one of said concentric springs, elongated postscarried by said plate and axially aligned with said bosses to confinelateral movement of the axis of said springs.

10. Brake system apparatus as defined in claim 9 further including meansdefining positive limits of spring compression disposing the ends ofsaid posts with only a slight spaced relation between the post ends anda related one of said bosses thereby retaining said springs within saidseats.

References Cited UNITED STATES PATENTS Wood 2671 20 2,673,483 3/1954Bird 188-170 X 3,101,133 8/1963 House et a1. 188--170 3,144,812 8/1964Rager et a1 9264 X 5 FOREIGN PATENTS 548,546 4/1932 Germany. 84,0618/1935 Sweden.

MARTIN P. SCHWADRON, Primary Examiner.

10 I. C. COHEN, Assistant Examiner.

1. BRAKE ACTUATING APPARATUS COMPRISING A CONNECTING MEMBER ADAPTED TOBE MOVED TO OPERATE A BRAKE SHOE BETWEEN BRAKE APPLYING AND BRAKERELEASING POSITIONS, A CYLINDER, A PISTON MOVABLE WITHIN THE CYLINDER TOMOVE THE MEMBER, SPRING BIASING MEANS PROVIDING A SOURCE OF STOREDENERGY TO DRIVE SAID MEMBER TO BRAKE APPLYING POSITION, SAID BIASINGMEANS INCLUDING AT LEAST TWO BANKS OF HELICAL SPRINGS WITHIN SAIDCYLINDER AND DISPOSED TO MOVE SAID PISTON IN BRAKE APPLYING DIRECTION, APLATE SEPARATING SAID BANKS AND MUTUALLY SUPPORTED BY BOTH, EACH